Transflective display device having a black/white or half-tone display in the reflecting operating mode

ABSTRACT

A transflective display device comprising a first transparent substrate for letting in light of a background lighting, whereby the first transparent substrate is provided with first electrodes. The display device also comprises a second transparent substrate for displaying graphic patterns, whereby the second transparent substrate is provided with second electrodes. An electro-optical material is provided, in particular, in the form of a liquid crystal layer between the first and the second transparent substrate. The display device additionally comprises pixel sections that are provided in overlapping areas of the respective first and second electrodes, have a respective reflecting element for reflecting light let in through the second substrate, and have a color filter element for filtering and permitting light, which is let in through the first substrate, to pass through in the direction of the second substrate. The reflecting element is placed on sides of the second substrate, and the color filter element is placed on sides of the first substrate. This enables, during the transmissive operating mode of the display device, a colored display of graphic patterns whereas during the reflective operating mode, a black/white display or half-tone display of a high contrast and high brightness is provided.

FIELD OF TECHNOLOGY

The present disclosure relates to a transflective display device whichprovides a color display in a transmissive operating mode in particular,while providing a black/white display or half-tone display in areflective operating mode.

BACKGROUND

An important component of a liquid crystal display (LCD) is a layer ofliquid crystals between two alignment layers. Molecules of liquidcrystal have an elongated-oval form and align themselves in parallelwithout external influence. It is also a property of liquid crystalsthat they align themselves to surfaces having a grooved structure in thedirection of the structure. As shown in FIG. 1, as a result of theirmolecular structure, liquid crystals LC in the nematic phase alignthemselves to surfaces OF1, OF2 having a grooved structure and acting asalignment layers here, and as a result of their mechanical properties,twist themselves in a spiral manner when they are introduced between twoalignment layers that are twisted by 90° (shown here by the arrows a andb of the surfaces OF1 and OF2). This arrangement is designated TwistedNematic (TN) if the angle of twist is 90°, and Super Twisted Nematic(STN) if the angle of twist is 270°. If an electrical field is appliedbetween the two layers, the liquid crystal molecules align themselvesalong the direction of the field.

In addition to the structure shown in FIG. 1, a liquid crystal displayalso requires two polarizers and at least two electrodes, an image dotsection being produced in the overlap area of said electrodes. If alight (e.g. from a background illumination) which has been polarized bythe first or rear polarizer P1 now hits the spirally arranged liquidcrystals LC, as shown in FIG. 2A, this light is rotated in itspolarization direction in accordance with the angle of twist of themolecules. It then hits the second or front polarizer P2 (analyzer),whose polarization direction is twisted by 90° in relation to that ofthe first polarizer P1. The light can therefore penetrate through to anobserver (in a downward direction in the figure).

If, as shown in FIG. 2B, an electrical field is generated by a voltagesource VOL and applied to the liquid crystal molecules LC via thealignment layers ARL (corresponding to the surfaces OF1 and OF2 fromFIG. 1), the liquid crystal molecules LC align themselves to theelectrical field accordingly. Light which now comes in from above ontothe liquid crystal arrangement that is illustrated in FIG. 2B is firstpolarized by the polarizer P1, then penetrates through the upperalignment layer ARL and then follows the orientation of the liquidcrystals again. In the present case, since the polarization plane of thelight is not rotated by 90° as it was in FIG. 2A, the light cannotpenetrate downwards, i.e. through the second polarizer P2. Therefore, bymeans of electrically controlling the arrangement of the liquidcrystals, it is possible to influence their optical properties(particularly in relation to transmissivity).

What has just been explained in relation to the FIGS. 2A and 2B is thecontrol of a single image dot section. A conventional liquid crystaldisplay device includes a multiplicity of such image dot sections,however, wherein graphical patterns such as alphanumeric characters,symbols, graphics, photos, etc. can be displayed on the liquid crystaldisplay device by means of selectively controlling said image dotsections. For this purpose, the liquid crystal display device includes afirst transparent substrate, e.g. made of glass, upon which a firstpolarizer is deposited. It also has a second transparent substrate uponwhich a second polarizer is deposited, whose polarization plane istwisted by 90° in relation to that of the first polarizer. There is alayer of liquid crystals between the two substrates. Furthermore,provision is made for a matrix-type arrangement of electrodes, e.g. rowelectrodes on the first substrate and column electrodes on the secondsubstrate. In the overlap area of such a row electrode and columnelectrode, it is then possible to define an image dot section which canbe specifically and electrically controlled. In relation to the controlof the individual image dot sections, a distinction is made between anactive matrix liquid crystal display (AMLCD) and a passive matrix liquidcrystal display (PMLCD). Since the individual image dot sections arecontrolled directly by a matrix-type arrangement of row electrodes andcolumn electrodes in the case of a PMLCD, it follows that in principleeach individual cell is only controlled for 1/(resolution=total numberof image dot sections) of the total time of the image display. Becausethe cells are in a voltage-free state for the remainder of the time, theliquid crystals must be configured in such a way that they arecorrespondingly slow-acting, in order to ensure that they do not revertduring the remaining time and thereby to prevent any loss of contrast orflimmer effects.

In the case of an AMLCD, however, each image dot section is controlledby a dedicated thin-film transistor (TFT) which stores the informationfor the relevant image dot section.

Since white light is normally used for the background illumination of aliquid crystal display device, said light must be filtered usingsuitable color filters in order to display color images. A specificcolor filter is assigned to each individual image dot section in thiscase, there being customarily three types of color filter, namely a redfilter, a yellow filter and a blue filter. Three image dot sections withthese three different color filters are then combined to form a pixel.

In addition to the previously described transmissive operating mode of aliquid crystal display device, in which light of a backgroundillumination comes through a first polarizer or a first substrate intothe display device and, after being influenced if necessary by means ofthe liquid crystal layer in an image dot section, is allowed out againthrough the second substrate or the second polarizer for the purpose ofdisplaying graphical patterns, there is also a reflective operating modein the case of a transflective display device. In this context, light ofa background illumination is not allowed in through the first polarizer(the first substrate), but instead ambient light comes through thesecond polarizer (the second substrate) into the display device, passesthrough the liquid crystal layer and is ultimately reflected by atransflective layer which is advantageously deposited on the firstsubstrate. In this case, this transflective layer has reflectionelements for reflecting light and also has transit openings or slots forallowing the passage of light (which comes from a backgroundillumination and must be allowed through in the direction of the secondsubstrate).

A liquid crystal display device having a conventional arrangement of theindividual components is described schematically below with reference toFIGS. 3 and 4, in which relevant cross-sectional views of a liquidcrystal display device are shown.

FIG. 3 shows a liquid crystal display device A1 in which three image dotsections BPA1, BPA2 and BPA3 (characterized by vertical broken lines)are represented with different color filters in each case FF1 (havingthe color red), FF2 (having the color yellow) and FF3 (having the colorblue) for the purpose of illustration. In this case, the relevant imagedot sections are produced in the overlap area of a first electrode E1and three electrodes E21, E22 and E23 which run perpendicular to saidfirst electrode. In this case, the electrodes are manufactured from atransparent material, e.g. indium tin oxide (ITO). The electrode E1 isarranged on a first transparent substrate S1, and a first polarizer P1is deposited on the opposite side of said first substrate. Theelectrodes E21, E22 and E23 are deposited on a second transparentsubstrate S2, and a second polarizer P2 is deposited on the oppositeside of said second substrate. Furthermore, reflection elements R1, R2and R3 are advantageously configured as part of a transflective layer onthe first electrode, wherein a relevant color filter FF1, FF2 and FF3 isprovided on a relevant reflection element. In this case, a part of arelevant color filter FF1, FF2 and FF3 overlaps a relevant reflectionelement, while a further part extends beyond the relevant reflectionelement. A layer of liquid crystals is then provided between the colorfilters FF1 to FF3 and the relevant second electrode E21 to E23 (thisbeing omitted for reasons of clarity in the drawing).

In a transmissive operating mode of the liquid crystal display A1 asshown in FIG. 3, in which light (characterized by three arrows runningdiagonally upwards) is provided by a light source for backgroundillumination, this light penetrates through the first polarizer P1 andthe first transparent substrate S1 into the liquid crystal display,where it hits not only the reflection elements R1 to R3, at which it isreflected back again, but also those parts of the relevant color filtersthat extend beyond the reflection elements. The normally whitebackground light (characterized by the letter “W” at the foot of eachrespective arrow) is filtered by these extending parts of the colorfilters, and can then be allowed out again through the secondtransparent substrate S2 and the second polarizer P2 (towards the top inthe figure) as a result of corresponding control of a relevant image dotsection (by means of the electrodes E1, E21, E22, E23).

FIG. 4 shows the same liquid crystal display device A1 as FIG. 3,wherein a reflective operating mode of the display device will now beexplained. It is evident from the figure that light from a backgroundillumination does not come in through the first polarizer P1 and thefirst substrate S1 in this case, but that ambient light (normally whiteambient light, characterized by the letter “W”) enters through thesecond polarizer P2 and the second substrate S2 into the display device,passes through the relevant second electrodes and the liquid crystallayer and ultimately arrives at a relevant color filter FF1 to FF3. Thelight now passes through a relevant color filter a first time on the way(in a downwards direction in the figure) to a relevant reflectionelement R1 to R3, is reflected at a reflection element and then passesthrough the color filter a second time, so that finally a filtered lightis allowed out of the display device or the second polarizer P2, saidlight corresponding to the color of the color filter it has just passedthrough.

A conventional display device of this type as per FIGS. 3 and 4 has thedisadvantage that, particularly in reflective mode, the display which ispresented by the display device at the outer surface of the polarizer P2appears very dark and is therefore difficult to read as a result of thefact that incoming ambient light must pass through a color filter twice.

The present disclosure therefore addresses the problem of creating adisplay device which is easily readable in both transmissive mode andreflective mode.

BRIEF SUMMARY

A display device is disclosed herein, having a first transparentsubstrate for letting in light of a background illumination, wherein thefirst transparent substrate is equipped with first electrodes. Thedisplay device also has a second transparent substrate for allowinglight through or out, with the light having been modified or influencedin the display device, wherein the second transparent substrate isequipped with second electrodes. An electro-optical material is providedbetween the first and the second transparent substrate. The displaydevice also has image dot sections which are provided at the overlappingareas of the relevant first and second electrodes and have in each casea reflection element for reflecting light which comes in through thesecond substrate and a color filter element for filtering the lightcoming in through the first substrate and allowing it to pass through inthe direction of the second substrate. In this case, a color filterelement can have a section or part which overlaps the reflection elementand a part which extends beyond the reflection element, wherein thisextending part can allow light to pass through the color filter elementfrom the first substrate in the direction of the second substrate. Inthis case, the reflection element is arranged on the side of the secondsubstrate and the color filter element on the side of the firstsubstrate.

Such an arrangement has the effect that, in the transmissive mode of thedisplay device, light can now enter into the display device through thefirst transparent substrate, arrives at a relevant color filter of animage dot section, is either blocked or allowed to pass through in thedirection of the second substrate in accordance with a control of theimage dot section by means of the electrodes, in order to provide on theouter side or outer surface of said second substrate a color displayincluding color graphical patterns for a user.

In the reflective operating mode, however, in which light is allowedinto the display device through the second transparent substrate, thelight after passing through the electro-optical material now arrivesdirectly at the relevant reflection elements of the image dot sectionsand is reflected by them. Once again, the light is then either blockedor allowed to pass out through the second substrate again in accordancewith the control of the image dot section by means of the electrodes, inorder to provide on the outer side of said second substrate a display(of graphical patterns) for a user. As a result of the fact that lightno longer passes through a color filter in the reflective mode, which itdoes in the prior art, the display device disclosed herein only providesa grayscale display (of graphical patterns) in the reflective mode underan exemplary embodiment. However, the contrast and the brightness of thedisplay is significantly improved using this type of configuration,thereby improving the readability of the display, whether it comprisescharacters, symbols, graphics or photographs.

Accordingly, the display device can furthermore include a firstpolarizer which is assigned to the first transparent substrate and isdeposited thereupon, and a second polarizer which is assigned to thesecond transparent substrate and is deposited thereupon and has apolarization plane that is perpendicular to that of the first polarizer.In this case, the polarizers can be deposited on the relevant innersurface (i.e. on the side of the electro-optical material) or outersurface of the relevant substrates.

Furthermore, the electro-optical material can comprise a layer of liquidcrystals.

In accordance with a further advantageous development, the firstelectrodes are arranged parallel to each other and extend in a firstdirection, while the second electrodes are likewise arranged parallel toeach other and extend in a second direction which is perpendicular tothe first direction. In this way, a matrix-type electrode arrangementwith column electrodes and row electrodes can be implemented, whereinthe image dot sections in the overlapping areas can be electricallycontrolled. In this case, the first and second electrodes advantageouslyconsist of a transparent material, e.g. indium tin oxide (ITO).

Furthermore, the display device is preferably developed as an activematrix liquid crystal display, such as a TFT (Thin Film Transistor)liquid crystal display, or as a passive matrix liquid crystal display,as well as a CSTN (Color Super Twisted Nematic) liquid crystal display.

The display device may alternately have its own light source which isarranged adjacently to the first transparent substrate or the firstpolarizer on the opposite side to the electro-optical material. Thismeans that the light source is arranged outside of the actual imagegenerating entity and is used to provide light that is required forcreating a display of graphical patterns in the transmissive mode of thedisplay device.

The color filter elements advantageously comprise the colors red, yellowand blue, wherein one color pixel is represented in each case by threeadjacent image dot sections having the colors red, yellow and blue.

In accordance with a further embodiment of the disclosure, an electricalapparatus is disclosed that comprises a display device as describedabove or advantageous developments thereof. In this way, it is possiblethat the electrical apparatus has an apparatus-internal light source forproviding a background illumination for the display device, wherein theapparatus-internal light source is arranged on the side of the firsttransparent substrate. In this case, a display device-internal lightsource can be omitted. The electrical apparatus is preferably developedas a mobile apparatus, in particular as a mobile telephone or mobileradio apparatus, as a portable computer such as a PDA (personal digitalassistant) or a clock, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The various objects, advantages and novel features of the presentdisclosure will be more readily apprehended from the following DetailedDescription when read in conjunction with the enclosed drawings, inwhich:

FIG. 1 illustrates a schematic illustration of liquid crystal moleculeswhich are arranged between two alignment layers;

FIGS. 2A and 2B illustrate a schematic of the main components of aliquid crystal display, in order to explain the control of the lightpassage depending on an electrical field which acts on a liquid crystallayer;

FIG. 3 is a schematic cross section view of a conventional transflectiveliquid crystal display which is currently being used in the transmissiveoperating mode;

FIG. 4 is a schematic illustration of the same display device as in FIG.3, wherein a reflective operating mode is shown in this case;

FIG. 5 is a schematic cross sectional view of a liquid crystal displayaccording to one embodiment, wherein a transmissive operating mode isillustrated;

FIG. 6 is an illustration of the liquid crystal display as in FIG. 5,wherein a reflective operating mode is shown;

FIG. 7 is a schematic illustration of an electrical apparatus which isimplemented in the embodiment of a mobile radio apparatus or mobiletelephone; and

FIG. 8 is a schematic illustration of an electrical apparatus which isimplemented in the embodiment of a small portable computer.

DETAILED DESCRIPTION

One exemplary embodiment of the present invention is described withreference to FIG. 5. In this case, FIG. 5 shows a schematic crosssectional view of the main components of a transflective liquid crystaldisplay device A2. Similar to the liquid crystal display device A1 inFIG. 3, the liquid crystal display device A2 comprises a firsttransparent substrate S1 and a second transparent substrate S2, betweenwhich is arranged an electro-optical material in the form of a liquidcrystal layer LC as shown in FIG. 5. Glass substrates are advantageouslyused as the transparent first and second substrates. A polarizer P1 isalso deposited on the outer surface of the first transparent substrateS1, while a first electrode E1 is deposited on the inner side. Apolarizer P2 is deposited on the outer surface of the second transparentsubstrate S2, while relevant electrodes E21, E22 and E23 are depositedon the inner surface. It should be noted here that the display device A2has further electrodes in addition to the electrodes that are visible inthe figure, i.e. further first electrodes that are arranged parallel toelectrode E1 on the first substrate S1 and further second electrodes arearranged parallel to the electrodes E21, E22 and E23 on the secondsubstrate S2. In this case, the first and second electrodes form amatrix-type structure with row electrodes and column electrodes.

Relevant image dot sections BPA1, BPA2 and BPA3 are implemented in theoverlap areas of the first electrode E1 and the second electrodes E21 toE23, where the image dot sections is characterized by broken verticallines. It should be noted that the image dot sections are not restrictedto the space between the electrodes, but relate to an area of thedisplay device, which area is individually controllable and has arelevant reflection element or color filter element. In this case, theimage dot section BPA1 includes a first reflection element R1 and afirst color filter element FF1 representing the color “red”, the secondimage dot section BPA2 includes a second reflection element R2 and asecond color filter element FF2 representing the color “yellow”, whilethe third image dot section BPA3 includes a third reflection element R3and a third color filter element FF3 representing the color “blue”. Inthis case, the relevant reflection elements have an almost 100%reflection property and are developed from aluminum, for example. Inthis case, it is possible that the reflection elements are developed aspart of a transflective layer which is deposited over the color filterelements. This transflective layer includes the reflection elements inthis case and, between the reflection elements, has transit openings orslots through which the light can pass. As illustrated in the figure,the color filter elements are arranged in such a way that they have anarea which overlaps the relevant reflection element and a part whichextends beyond the reflection elements. It is characteristic of theillustrated embodiment that the reflection elements are arranged on theside of the second substrate, while the color filter elements arearranged on the side of the first substrate, i.e. on the entry side oflight from a background illumination (from below in the figure). Asshown in the figure, it is conceivable to deposit the relevant colorfilter elements on the first electrode (or electrodes), while thereflection elements (or the transflective layer) are deposited on thecolor filter elements.

If the liquid crystal display device A2 is now operated in thetransmissive operating mode as shown in FIG. 5, light (characterized bythree arrows running diagonally upwards and leftwards) from a lightsource LQ for background illumination is allowed into the display devicefrom below in the figure through the first polarizer P1, penetrates thetransparent substrate S1 and the first electrode E1 and arrives at arelevant color filter element FF1 to FF3. The light source LQ, which isarranged below the actual imaging part of the liquid crystal displaydevice A2 in the figure, i.e. on the side of the first transparentsubstrate S1 or the first polarizer P1, can have e.g., one or more LEDs(LED: light-emitting diode) or an optical conductor which receives lightfrom an LED or a tubular lamp and supplies it to the imaging part asshown in the figure. The normally white light of the light source orbackground illumination (characterized by the letter W) at the origin ofan arrow representing a background light is appropriately filtered in arelevant color filter element FF1 to FF3 and then passes through thelayer LC of liquid crystals, the relevant second electrodes E21 to E23and the second transparent substrate, and emerges from the displaydevice through the second polarizer P2 in the color of the color filterthrough which it passed. This presupposes that the image dots BPA1 toBPA3 are controlled via the electrodes E1 or E21 to E23 in such a waythat light can pass through.

This means that in this case of the transmissive operating mode, inwhich a light source for background illumination is provided on the sideof the first substrate S1 or the first polarizer P1, a color display andcolor graphical patterns are provided on the side of the secondsubstrate or its assigned second polarizer. The three image dot sectionsBPA1, BPA2, BPA3 which are illustrated by way of example in the figurerepresent a (color) pixel in this case.

With reference to FIG. 6, there now follows an explanation of areflective operating mode of the display device which was previouslydescribed in FIG. 5. In order to improve the illustration, FIG. 6 onlyincludes those reference signs that are required for understanding. Incontrast to the transmissive mode as shown in FIG. 5, no light of abackground illumination penetrates from the side of the first polarizerP1 or the first substrate S1 into the display device A2 in thereflective mode, i.e. in contrast to the transmissive mode, the lightsource LQ is switched off in the reflective mode. Instead, an ambientlight (normally white ambient light) which is characterized by theletter W now penetrates from above through the second polarizer P2 intothe display device A2, passes through the second transparent substrateand the relevant second electrode and the layer LC of liquid crystals,and finally arrives at projecting or extending parts of the color filterelements, which it simply passes through, and at the relevant reflectionelements R1, R2 and R3. The light is directly reflected at thesereflection elements, without having to pass through a relevant colorfilter element twice as it must in the prior art (cf. FIG. 4). Dependingon the control of an image dot section via the first and secondelectrodes, the white light which entered the liquid crystal displaydevice A2 is allowed out again as white light, or no light is allowedout in an image dot section when a corresponding electrical field isapplied to the liquid crystal layer LC (characterized by the letters B/Wfor black (no light) or white (light) at the end of the exit part).

This means that, instead of a color display with color graphicalpatterns, a black/white display or grayscale display is provided on theouter surface of the second polarizer P2 which is assigned to the secondsubstrate (i.e. on the display surface) in the reflective operating modeof the display device A2. As mentioned above, since the incoming ambientlight in the reflective mode of the display device does not have to passthrough a color filter element twice as it must in the prior art (oncebefore the reflection at a reflection element and once after thereflection at the reflection element), the intensity of the light isattenuated less and the display device A2 provides a black/white displayor grayscale display with greater brightness and higher contrast,thereby improving the readability of graphical patterns such as symbols,characters, graphics or images. This means that, by switching off thebackground illumination (e.g. manually by a user or automatically by acontrol device if a charge of the battery supplying the display deviceor background illumination falls below a specified level), it ispossible to select a current-saving (reflective) mode which nonethelessallows a good readability of the display. It is therefore possible toextend the service duration of an electrical apparatus comprising thedisplay device A2.

It can therefore be stated in summary that, by means of the specialconfiguration of the image dot sections, in which a relevant reflectionelement is arranged on the side of the second substrate and thecorresponding color filter element on the side of the first substrate oron the side of the light source LQ, a color display is provided in thetransmissive mode (with the light source switched on), while ablack/white display or a grayscale display with high brightness and highcontrast is provided in the reflective mode (with the light sourceswitched off).

A display device in accordance with the present disclosure can be usedin an electrical apparatus as illustrated schematically in theembodiments shown in FIGS. 7 and 8.

A display device AZ according to the embodiments (e.g. the displaydevice A2) can be provided in an electrical apparatus EG1 which isdeveloped in the form of a mobile radio apparatus or mobile telephone asshown in FIG. 7.

However, a display device AZ according to the present invention (e.g.the display device A2 again) can also be installed in an electricalapparatus EG2 in the form of a portable computer (particularly in theembodiment of a PDA) as shown in FIG. 8.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present disclosureand without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1-11. (canceled)
 12. A display device comprising: a first transparentsubstrate having first electrodes; a second transparent substrate havingsecond electrodes; an electro-optical material, provided between thefirst and the second transparent substrate; a background illuminationwhich is arranged adjacently to the first transparent substrate on theopposite side to the electro-optical material and is designed to emitlight in the direction of the first transparent substrate; image dotsections, provided at overlapping areas of the relevant first and secondelectrodes, wherein each image dot section includes a reflection elementfor reflecting light which comes in through the second transparentsubstrate, and a color filter element for filtering the light coming inthrough the first transparent substrate and allowing it to pass throughin the direction of the second substrate; and a display surface arrangedon the opposite side of the second transparent substrate to theelectro-optical material, wherein the reflection element is orientedtowards the second substrate and the color filter element is orientedtowards the first substrate, in order to provide a color display on saiddisplay surface in a transmissive mode of the display device, in whichlight is emitted by the background illumination from the firsttransparent substrate through the relevant color filter elements to thesecond transparent substrate, and to provide a colorless display in areflective mode, in which light coming in through the second substrateis reflected back to the second transparent substrate directly by therelevant reflection elements.
 13. The display device according to claim12, further comprising a first polarizer which is deposited on the firsttransparent substrate, and a second polarizer which is deposited on thesecond transparent substrate and has a polarization plane that isperpendicular to that of the first polarizer.
 14. A display deviceaccording to claim 12, wherein the electro-optical material comprises alayer of liquid crystals.
 15. A display device according to claim 12,wherein the first electrodes are arranged parallel to each other andextend in a first direction, while the second electrodes are likewisearranged parallel to each other and extend in a second direction whichis perpendicular to the first direction.
 16. A display device accordingto claim 12, wherein the first and second electrodes are made of atransparent material.
 17. The display device according to claim 12,wherein the display device is an active matrix liquid crystal display,being one of a TFT liquid crystal display, a passive matrix liquidcrystal display, and a CSTN liquid crystal display.
 18. The displaydevice according to claim 12, wherein the relevant color filter elementscomprise the colors red, yellow and blue.
 19. The display deviceaccording to claim 18, wherein one color pixel is represented in eachcase by three adjacent image dot sections having the colors red, yellowand blue.
 20. The display device according to claim 12, wherein hedisplay device is incorporated into an electrical apparatus.
 21. Thedisplay device according to claim 12, wherein the display device isincorporated into a mobile apparatus.
 22. The display device accordingto claim 12, wherein the display device is incorporated into a mobiletelephone, a portable computer or clock.